Solid oxide fuel cells (SOFCs) have been considered one of the promising candidates for the next generation of power sources due to their high electrical and thermal efficiencies, environmentally benign characteristics, and fuel flexibility. For the last century, work has been focused on improving the power output and producing compact designs for SOFCs.
Planar and tubular cell geometries are the two main SOFC designs. Tubular SOFCs, especially micro-tubular SOFCs, have attracted much attention due to their ease in sealing and gas manifolding, tolerance for thermal cycling, quick start up and shut down capability, and potential for high volumetric power density. These advantages make them suitable for a variety of applications such as cogeneration as well as power sources for transportation and portable devices.
On the other hand, SOFCs have been reported to be reversible and can be operated in solid oxide electrolysis cells (SOECs) as a mode for hydrogen (H2) generation. Tubular SOECs offer a potentially viable alternative for large scale and high-purity hydrogen generation by splitting water into hydrogen and oxygen. In addition, production of syngas (CO+H2) using high temperature co-electrolysis of steam and CO2 has the promise to create a new paradigm in CO2 sequestration.
Although theoretical and laboratory studies of tubular SOFCs have been pursued for over 40 years, the design and manufacture of tubular SOFCs are still key technical issues that have not been satisfactorily resolved. Great attention has been paid to the phase-inversion method to prepare asymmetric membranes widely used in fiber, gas separation etc., for its simple process and the relatively inexpensive equipment involved. Recently the phase-inversion process has been applied in the SOFC field to fabricate ceramic hollow fiber electrolyte, where dense electrolyte and porous electrode bilayers can be produced from a co-sintering step.
Consequently, a novel approach to fabricate economical high performance tubular SOFC is desirable.